Non Patent Literature 1 below describes that resveratrol and piceatannol, which are polyphenol compounds derived from grape, have effects of inhibiting melanin production by melanin-producing cells. However, to perform a test for confirming the effects, a commercially available reagent is used, and the literature does not describe that a composition containing piceatannol or the like derived from a natural material such as grape is obtained.
Meanwhile, Patent Literature 1 below describes that resveratrol is concentrated and collected inexpensively, selectively, and efficiently from an extract of roots of Reynoutria japonica Houtt. var. japnica. Further, Patent Literature 2 below describes a cowberry extract containing resveratrol. Still further, Patent Literatures 3 and 4 below describe an extract of passion fruit (Passifloraceae, Passiflora sp.), in particular, an extract of passion fruit pericarp and use of the extract in foods, dietary supplements, and medical fields.
However, none of the arts described in the above-mentioned literatures provides a composition, which is obtained from a natural material and contains piceatannol at a high content.